Liquid seal compressors

ABSTRACT

A liquid seal compressor has a vaned impeller which runs on one side of a distribution plate so that the cellular chambers between the vanes sweep a zone on said plate. Inlet and outlet apertures for working fluid and sealing liquid are formed within said zone in said plate. The edge between the radially outer boundary of the outlet aperture and the side of said plate facing the impeller is rounded or bevelled and preferably a narrow straight edge or chamfer is formed from said side of the plate to the start of the rounded or bevelled portion.

United States Patent Segebrecht 51 Dec. 26, 1972 [54] LIQUID SEAL COMPRESSORS [72] Udo Segebrecht, Ellerbrook, Germany Siemen & Hinscb mbl-l, ltzehoe/I-lolstein, Germany Feb. 23, 1971 Inventor:

Assignee:

Filed:

Appl. No.:

U.S. Cl ..417/68 Int. Cl ..F04c 19/00 Field of Search 417/68, 69; 418/15; 259/95,

259/96; 233/47 R; 415/213 T, 199 T, 53 T References Cited UNITED STATES PATENTS l/1966 Segebrecht ..4l7/68 X 2,025,959 12/1935 Seibold et al ..4l7/68 Primary Examiner-Carlton R. Croyle Assistant Examiner-Richard E. Gluck Attorney-John Lezdey [57 ABSTRACT 4 Claims, 3 Drawing Figures PATENTEDmzsmz uvo SIEGEBREQHT 92 BY: v %FY LIQUID SEAL COMPRESSORS The invention relates to a liquid seal compressor with at least one vaned member or impeller, whose cellular chambers are open in respect of a distribution plate or plates each containing an outflow aperture for the fluid or impelling medium and a part of the operating liquid, the said outflow aperture lying laterally to the vaned member in the zone of the vanes.

The expression compressors as used herein is to be understood to refer to single and multi-stage compressors and also to the individual stages of a multi-stage compressor.

Liquid seal compressors or the individual stages of a multi-stage liquid seal compressor are each designed hydraulically for a given quantity of impelling medium and a given pressure ratio. These power conditions determine first of all the dimensions of the vaned member or impeller chamber, namely width and diameter of the vaned member, number of vanes, vane lead curvature, diameter of the housing, and furthermore they also determine the size and shape of the throughflow apertures for the fluid or impelling medium. In particular the pressure conditions to be overcome by the stage are critical for their construction.

However the compressor does not always act at its optimum operating point for which it is designed, in fact under the most commonly occurring conditions it may have to operate over a widely varying pressure range. This means that it also has to work over pressure ranges for which it is not optimally designed, and in which therefore it cannot operate at optimum capacity. Apart from a reduction in power output this makes itself felt in a correspondingly unfavorable power ratio and consequently a less favorable degree of efficiency.

The pressure ratio of the compressor is critical for the length of the troughflow apertures for the impelling medium in the peripheral direction. In order to operate under varying pressure conditions in the most economic manner possible, it is known to cover up a part of the outflow aperture with automatic valves, which automatically adapt the length of the outflow aperture to the prevailing operational conditions. Furthermore it has been found that the optimum course of the radially outer limit of the outflow aperture differs for different pressure conditions.

With a high pressure ratio a very large quantity of operating liquid is fed to the compressor and it is accordingly necessary to eject a corresponding quantity of this operating liquid on the pressure side of the compressor through the outflow aperture together with the impelled gas. This involves the possibility of extremely high flow velocities occurring at the sharp outer boundary edge of the outflow aperture directly next to the vaned member or impeller wheel, so that local cavitation can arise at this position with the known results of damage and disturbance. It may also happen that there is not a sufficient discharge of the excess liquid through the outflow aperture, so that a damming-up of the liquid occurs in the zone of the highest degree of compression, the peak as it is termed, the liquid ring or seal impinging right on the hub. This phenomenon leads to a high power loss of the compressor in this operational range, and to a high loading of the shaft, which may even result in a fracture of the shaft.

Consequently, although with a high pressure ratio the dischargeof the excess operating liquid should be as unimpeded and as easy as possible, with a lower pressure ratio it is desirable for as little liquid as possible to flow out with the impelled gas from the outflow aperture, because in this operational range the pump is fed with only a comparatively little operating liquid and with too great a loss of liquid through the outflow aperture the impelling action is deleteriously affected.

One object of the invention is to provide a liquid seal compressor which is designed to meet these diametrically opposed requirements.

According to the invention the solution of the problem is found in bevelling off or rounding off the radially outer boundary edge of the outflow aperture or apertures at the side facing the vaned member or impeller wheel. I

' If the compressor is working at low' pressure and only a small quantity of operating liquid is fed to it, then only a small quantity of the operating liquidescapes with the impelled gas out of the vaned member cells through the outflow aperture. The rounded-off or bevelled off radially outer boundary edge apparently has the effect of holding back the necessary quantity of operating liquid in the impelling chamber of the pump. On the other hand in the case of a high pressure ratio the rounding-off or bevelling-off appears surprisingly to have the very opposite effect, that is to say, when a large quantity of liquid is fed to the compressor, the cavitation phenomena vanish and it is less easy for a damming-up of the liquid to occur in the peak, which must be adduced to a considerable discharge of liquid.

It has been found particularly advantageous, in a particular embodiment of the invention, to provide a narrow straight edge or chamfer at the radially outer boundary of the outflow aperture before the beginning of the bevelling or founding. As the side of the distribution plate or boundary wall facing the vaned member still always has to be machined, since between it and the vaned member only'a very small gap remains, this narrow straight edge of chamfer brings the advantage that the radially outer contour of the radially outer boundary edge of the outflow aperture remains independent of the machining. If this chamfer or edge is not present then high requirements must be set for the tolerances on casting and finish; if it is provided, then the usual tolerances can be accepted for casting and finishing. It has been found that this narrow straight edge or chamfer, the width of which should be less than a millimeter, does not have any deleterious effect.

It should also be mentioned that the rounding or bevelling of the radially outer boundary of the outflow aperture need not absolutely necessarily extend, viewed in the peripheral direction, over the whole width of the outflow aperture. it may be sufficient if it extends over a portion only of the outflow aperture, particularly over the part first reached in rotation by the vanes.

The invention will now be described in greater detail, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 shows a plan view of the lateral boundary wall of a varied member or impeller of a liquid-seal/gas pump with inlet and outlet apertures for the impelling medium, and

FIGS. 2 and 3 show sections taken along the line A-B in FIG. 1.

In FIG. 1 the vaned member is presumed to be lying in front of the plane of the drawing, as indicated in chain line, and comprises a hub 4 and vanes 5. The impelling medium arrives in the cells between the vanes of the vaned member through an inlet aperture 2 and leave the varied member cells through an outflow aperture 3 lying laterally to the vaned member, arranged radially in the zone of the vanes. Both apertures 2 and 3 are located in a wall or distribution plate arranged laterally to the vaned member or impeller wheel.

The radially outer boundary edge 3a of the outflow aperture 3 is provided, as can be clearly seen in FIGS. 2 and 3, with a rounding-off or bevelling-off 3c.. The rounding-off or bevelling-off 30 then finally opens into the edge 3b of the outflow aperture extending perpendicularly to the plane of the vaned member. I

FIGS. 2 and 3 also show the preferred feature of a narrow straight edge or chamfer 3a, which is provided at the radially outer boundary of the outflow aperture 3 before the beginning of the bevelling-off or roundingoff 30 on the side nearest the vaned member.

What is claimed is:

1. In a liquid seal compressor comprising at least one vaned impeller having cellular chambers defined by the vanes thereof, at least one distribution plate onto which said cellular chambers open and having on one side a zone swept by said chambers, said distribution plate being axially beside said impeller and having and inflow aperture and an outflow aperture within said swept zone, said outflow aperture defined by radially inner and outer boundary edges the improvement that said radially outer boundary edge of said outflow aperture is bevelled-off at said one side of the distribution plate whereby when the compressor operates at a high pressure ratio there is substantially no cavitation at the outflow aperture.

2. In a liquid seal compressor comprising: at least one vaned impeller having cellular chambers defined by the vanes thereof, at least one distribution plate onto which said cellular chambers open and having on one side a zone swept by said chambers, said distribution plate being axially beside said impeller, and having an inflow aperture and an outflow aperture within said swept zone, said outflow aperture defined by radially inner and outer boundary edges the improvement that said radially outer boundary edge of said outflow aperture is rounded-off at said one side of the distribution plate whereby when the compressor operates at a high pressure there is substantially no cavitation at the outflow aperture.

3. In a liquid sealcompressor comprising: at least one vaned impeller having cellular chambers defined by the vanes thereof, at least one distribution plate onto which said cellular chambers open and having on oneside a zone swept by said chambers, an inflow aperture in said distribution plate, and an outflow aperture in said distribution plate within said swept zone, said outflow aperture defined by radially inner and outer boundary edges the improvement that said radially outer boundary edge of said outflow aperture is bevelled off at said one side of the distribution plate and a narrow straight edge extends at said radially outer boundary edge from said one side of the distribution plate to the beginning of the bevelled position.

. In a llqllld seal compressor comprising: at least one vaned impeller having cellular chambers defined by the vanes thereof, at least one distribution plate onto which said cellular chambers open and having on one side a zone swept by said chambers, an inflow aperture in said distribution plate, and an outflow aperture in said distribution plate within said swept zone, said outflow aperture defined by radially inner and outer boundary edges, the improvement that said radially outer boundary edge of said outflow aperture is rounded off at said one side of the distribution plate and a narrow straight edge extends at said radially outer boundary edge from said one side of the distribution plate to the beginning of the rounded portion. 

1. In a liquid seal compressor comprising at least one vaned impeller having cellular chambers defined by the vanes thereof, at least one distribution plate onto which said cellular chambers open and having on one side a zone swept by said chambers, said distribution plate being axially beside said impeller and having and inflow aperture and an outflow aperture within said swept zone, said outflow aperture defined by radially inner and outer boundary edges the improvement that said radially outer boundary edge of said outflow aperture is bevelled-off at said one side of the distribution plate whereby when the compressor operates at a high pressure ratio there is substantially no cavitation at the outflow aperture.
 2. In a liquid seal compressor comprising: at least one vaned impeller having cellular chambers defined by the vanes thereof, at least one distribution plate onto which said cellular chambers open and having on one side a zone swept by said chambers, said distribution plate being axially beside said impeller, and having an inflow aperture and an outflow aperture within said swept zone, said outflow aperture defined by radially inner and outer boundary edges the improvement that said radially outer boundary edge of said outflow aperture is rounded-off at said one side of the distribution plate whereby when the compressor operates at a high pressure there is substantially no cavitation at the outflow aperture.
 3. In a liquid seal compressor comprising: at least one vaned impeller having cellular chambers defined by the vanes thereof, at least one distribution plate onto which said cellular chambers open and having on one side a zone swept by said chambers, an inflow aperture in said distribution plate, and an outflow aperture in said distribution plate within said swept zone, said outflow aperture defined by radially inner and outer boundary edges the improvement that said radially outer boundary edge of said outflow aperture is bevelled off at said one side of the distribution plate and a narrow straight edge extends at said radially outer boundary edge from said one side of the distribution plate to the beginning of the bevelled position.
 4. In a liquid seal compressor comprising: at least one vaned impeller having cellular chambers defined by the vanes thereof, at least one distribution plate onto which said cellular chambers open and having on one side a zone swept by said chambers, an inflow aperture in said distribution plate, and an outflow aperture in said distribution plate within said swept zone, said outflow aperture defined by radially inner and outer boundary edges, the improvement that said radially outer boundary edge of said outflow aperture is rounded off at said one side of the distribution plate and a narrow straight edge extends at said radially outer boundary edge from said one side of the distribution plate to the beginning of the rounded portion. 